I very much doubt whether projects created in the Avanquest software can be imported and opened in any other web design program. The nature of these project files is that they are (almost) exclusively "proprietary", i.e., designed to open ONLY in the program they were created in.
Magix Web Designer, like your Avanquest software, is a web-layout and publishing program; the .html and all other web files are created when you export and publish your finished site. Once created, without a very great deal of work, those .html and other web files cannot be directly imported into another program. The only solution I know of in such circumstances is to "copy and paste" text, images etc., to your new design program and to be prepared for a lot of hard work as you try and make things "fit" and "work".